Vitamin D reduces the risk of different types of cancer and improves the effectiveness of immunotherapies due to its action on the intestinal microbiota, according to research led by the Francis Crick Institute in London.
Researchers have discovered that vitamin D increases the population of Bacteroides fragilis, a type of intestinal bacteria that strengthens the immune system's ability to prevent the appearance of cancer and stop it once it has appeared. The exact way in which these bacteria strengthen the immune system has not yet been clarified.
With the data available so far, “we do not advocate any type of vitamin D-based intervention for the prevention or treatment of cancer; “This is basic science research,” immunobiologist Caetano Reis e Sousa, director of the work, warns in an email to La Vanguardia.
Even so, “our data [have] potential clinical and public health applications,” the researchers write in the journal Science, where they present their results today.
The research analyzed data from one and a half million people in Denmark who had their blood level of vitamin D measured. In subsequent years, those with lower levels had a higher risk of developing cancer. This result adds to that of previous studies, with fewer participants and that were considered inconclusive, which had already pointed to a possible relationship between vitamin D and a lower risk of colorectal, breast, prostate and pancreatic cancers.
In a second analysis of cells from 2,678 patients with different types of cancer, it has been observed that lower vitamin D activity is associated with shorter survivals.
In cases in which immunotherapy drugs are administered, analyzed in another group of more than a thousand patients, a vitamin D deficiency has also been associated with less effectiveness of the treatment.
The key lies in the action of vitamin D on the intestinal microbiota, as researchers have discovered in experiments with mice. They have shown that dietary vitamin D acts on colonic epithelial cells in a way that increases the population of B. fragilis bacteria. They have subsequently shown that these bacteria, to which previous studies had already attributed an oncoprotective effect, enhance immunity against cancer.
Mice fed a diet enriched in vitamin D have shown a lower propensity to develop tumors and a better response to immunotherapy treatments. The same effect has been observed in mice that directly ingested bacteria of the B. fragilis species.
“This could one day be important for cancer treatment in humans, but we don't know how or why vitamin D has this effect through the microbiome; We must investigate more,” declares Caetano Reis e Sousa in a statement released by the Francis Crick Institute.
“Vitamin D supplements can be a relatively simple dietary intervention to start testing,” argue Fabien Franco and Kathy McCoy, researchers at the University of Calgary (Canada) who were not involved in the study, in an analysis article in Science .
Few foods contain vitamin D in sufficient quantity to provide the amount that the human body needs. Those that have the most are oily fish (such as sardines and salmon, among others) and foods to which vitamin D supplements are added (such as some cereals). It is also found to a lesser extent in egg yolks, livers, cheeses and mushrooms.
The body produces much of the vitamin D it needs in the skin thanks to exposure to solar radiation, which is why vitamin D deficiency is more common in northern Europe than in Mediterranean countries. But “it is not necessary to sunbathe to enhance this process,” since a little solar radiation is enough, warns Nisharnthi Duggan, from Cancer Research UK, one of the organizations that participated in the research. Too much vitamin D can even be toxic.
